#!/usr/bin/env node 
const{Readbale}=require('stream');
//const Readable=require('stream').
const rs=new Readable();
let c='a'.charCodeAt(0);
rs_.read=()=>{
 // rs.push('hello');
 // rs.push(null);
  rs.push(String.fromCharCode(c++));
  if(c==='z'.charCodeAt(0)+1){ rs.push(null);
}
rs.pipe(process.stdout)
